Abstract
Existing methods of water treatment are faced with the problem of accompanying secondary contaminants introduced by the process of purification or neutralization of the primary contaminants. Polyhexamethyleneguanidine (PHMG) is effective for heavy metals ions removal and reduces environmental pollution. The efficiency of polyhexamethyleneguanidine as a complexing agent, biocide and flocculant is directly related to the ability to bind heavy metal ions, and the stronger the metal aggregates with the polyelectrolyte, the better the water purification and the easier the precipitation. The assumption was confirmed about the complex reaction of polyhexamethyleneguanidine with ions of heavy metals (Pb, Cd, Cu, Zn), the features of which are determined by the electron configuration of these metals: Pb(II) and Cd(II) are characterized by the formation of associates on the basis of sparingly soluble basic salts, and the direct coordination reaction of the metal ion with the PHMG nitrogen is more characteristic of Cu(II) and Zn(II). The products of the reaction of salts of heavy metals (Pb, Cd, Cu, Zn) with polyhexamethyleneguanidine were investigated by IR spectroscopy. The bonds, confirming the formation of stable compounds were revealed in the samples. The level of bond strength and the method of metal binding with polyelectrolyte were studied by polarography. The stability constants and coordination numbers of coordination compounds were computed, which allows predicting their stability in the process of technological transformations. This makes it possible to recommend PHMG for use in multistage processes of water purification from heavy metals.
Highlights
Polarography and IR spectroscopy revealed the reaction of polyhexamethyleneguanidine to form sparingly soluble basic salts for Pb(II) and Cd(II), metal compounds for Cu(II) and Zn(II) through the reaction of its ion with the PHMG amino group to form fairly soluble compounds
It was found that the Zn(ІІ)-PHMG complex with a variable coordination number р=(1÷0,3), determined by polarography, may indicate the impact of the PHMG adsorbed on the cathode and the effect of the PHMG molecule coiling on the formation of associates
Using the method of IR spectroscopy, identification of Me-PHMG-associates was carried out, the types of bonds involved in the formation of the studied compounds were identified
Summary
The anthropogenic impact on water resources is becoming more active. Noncompliance with sanitary norms by enterprises, outdated treatment technologies of waste water discharged into surface waters cause a high content of toxic substances in the environment. The studies of the reaction of heavy metal compounds with multifunctional flocculants, including polyhexamethyleneguanidine hydrochloride (PHMG HC) for improving water treatment technologies are relevant. In the analysis of the methods of heavy metal ions removal from solutions, we should note two main trends: the metal ion transfer to a sparingly soluble state [1], and the consolidation of the pollutant ion binding associates [2] The fulfillment of these conditions greatly facilitates the process of coagulation, flocculation, filtering and precipitation. The research [10] shows the use of the modified adsorbent which is PHMG chemically sealed on the surface of amine-containing silica gel The authors use this adsorbent for removal of V(V), Mo(VI), W(VI), Cr(VI) ions from aqueous solutions. The products of its reaction with heavy metal ions a priori cannot be identified without experimental research
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